The utility model relates to a semiautomatic blackboard eraser for wiping blackboards in classrooms, belonging to a teaching appliance. The structure is characterized in that a bar shaped board wiper and a lever are together fixed on a bar rack. Moreover, both ends of the bar rack are provided with pulleys. The pulleys are arranged on guide rails. Two bar racks are fixedly connected by a handle. The handle pulled, the pulleys can move. The lever can be compacted for the board wiper to be stressed. Thus, the purpose of wiping dust on the blackboards is reached. The utility model has the advantages of reasonable structure, low cost, time saving, labor saving and high work efficiency. In addition, the teachers' health is protected.